The present invention relates to a device for the automatic measurement of tunnel cross- and longitudinal-sections by means of lasers.
It is already known in this art to measure tunnel profiles with photographic methods; however, this procedure proves to be very slow because first of all there have to be taken a great number of photos, and, then each of them has to be measured by a coordinatograph in order to obtain the profile of the tunnel.
Also known in this art is a purely mechanical device comprising a certain number of sensing elements; this kind of device, heavy and expensive, cannot be used for electrified railway tracks.
Another prior art arrangement utilizes two laser beams forming a triangle whose one vertex is directed towards the tunnel wall; if the two sides of the triangle do not meet, it is possible either to measure the distance between the two spots or to shift the base until the two sides of the triangle meet. This device has some disadvantages: It must be ascertained if the two beams meet and then the base must be mechanically shifted. A laser producing two beams must be specially constructed or there must be two of them. In particular, this device can be hardly used for simultaneously measuring several longitudinal sections. If transversal sections have to be obtained as well, a conventional photographical method must be used.